Technical Field
The present invention relates to a friction material with low environmental load using a carbon neutral plant-derived material as a raw material, and particularly to a friction material to be used for brake pads, brake linings, clutch facings and the like for automobiles, railway vehicles, industrial machines and the like.
Background Art
A friction material used for brakes and clutches includes, for example, materials such as a fibrous base material for exerting a reinforcing action, a friction adjusting material for imparting a friction action and adjusting its friction performance and a binder for integrating these components.
A problem of global warming due to an increase of a carbon dioxide concentration in atmospheric has recently been becoming a global problem, and techniques for reducing carbon dioxide emissions have been developed in various industrial fields. Also in the field of friction materials, consideration has been needed for wear powder generated from the friction materials and environmental load caused by the friction materials discarded, from the viewpoint of environmental preservation. Under these circumstances, it has been attracting attention to use carbon neutral plant-derived materials. For example, a lignin, which is a polyphenol much contained in wood and the like, is produced as a by-product when obtaining cellulose in the pulp production, so that there have been attempts to effectively utilize the lignin.
Patent Document 1 describes that noise, wear and sulfurous odor can be reduced by replacing about 1 to 30% by weight of a phenol resin, which is a binder component in a friction material composition, with an organosolv lignin substantially free from sulfur and low in water solubility.
Patent Document 2 describes a lignin-modified novolac type phenolic resin and a production method thereof.
Patent Document 1: JP-T-11-513726 (the term “JP-T” as used herein means a published Japanese translation of a PCT application)
Patent Document 2: JP-A-2008-156601